1. Field of the Invention
The present invention relates to a method of simulating a semiconductor circuit such as a transistor, an apparatus performing the method, and a recording medium storing a program performing the simulation method.
More particularly, the present invention relates to a method of simulating a semiconductor circuit which can effectively perform the simulation by a Monte Carlo method, even if the distribution of the semiconductor circuit's device parameters or the semiconductor circuit's process parameters, which affect the characteristics of the semiconductor circuit, is not a normal distribution, an apparatus thereof and a recording medium storing the method.
Also, more particularly, the present invention relates to a method of simulating a semiconductor circuit that can have a shortened processing time even if the number of parameters used for simulating the characteristics of the semiconductor circuit is large, an apparatus thereof, and a recording medium storing the method.
2. Description of the Related Art
During the development and design of the semiconductor circuit such as a transistor, the simulation of a semiconductor circuit is important for estimation (prediction) of the deviation of the device characteristics such as the deviation of a threshold voltage V.sub.th, analysis of the characteristics and understanding of the distribution of the electric field in the semiconductor circuit. In the simulation, process control parameters and profile dimensions such as a gate length are varied on the basis of the deviation of the production processes.
When process parameters are assumed to be in a normal distribution, the prediction of the deviation of the device characteristics uses a Monte Carlo method. As such, simulation software for a semiconductor circuit, PDFAB by PDF Solution Inc. and VMFab by SILVACO are on sale and have been extensively used. Such simulation software are limited to use when the deviation of the semiconductor circuit's characteristics is a normal distribution. In actual production processes, the deviation of the semiconductor circuit characteristics is not subjected to a normal distribution. Therefore, such known simulation software suffers from the disadvantage of an inaccurate simulation.
In addition to the above disadvantage, such known simulation software suffers from the disadvantage of a long processing (simulation) time. In such simulation software, when the number of the deviations, is n, 10.sup.n of the repeat (iteration) of the simulation is required, and thus if the number of the deviations is increased the simulation time will be very long. For example, when the characteristic calculation of 100 times for one deviation is carried out, and the number of the deviations is three, the loop calculation of one million times is needed, and the calculation time is over 100 hours.
To shorten the simulation time, the calculation number for each parameter should be reduced; however, such known simulation software can not greatly shorten the simulation time, and suffers from the disadvantage of inaccuracy in the simulation results.